In the semiconductor device manufacturing industry, device manufacturers have managed to transition to more closely toleranced process and materials specifications by relying on process tool manufacturers to design better and/or faster process and hardware configurations. However, as device geometries shrink to the nanometer scale, complexity in manufacturing processes increases, and process and material specifications become more difficult to meet.
A typical process tool used in current semiconductor manufacturing can be described by a set of several thousand process variables. The variables are generally related to physical parameters of the manufacturing process and/or tools used in the manufacturing process. In some cases, of these several thousand variables, several hundred variables will be dynamic (e.g., changing in time during the manufacturing process or between manufacturing processes). The dynamic variables, for example, gas flow, gas pressure, delivered power, current, voltage, and temperature change based on, for example, a specific processing recipe, the particular step or series of steps in the overall sequence of processing steps, errors and faults that occur during the manufacturing process or changes in parameter values based on use of a particular tool or chamber (e.g., referred to as “drift”).
One way to control the manufacturing process is to specify a set of model output values that defines the values of ideal parameters occurring during the manufacturing process. The actual output values of the manufacturing process are then compared to the model output values to determine if the actual output values are consistent with the model output values. This comparison is performed manually by a process engineer to determine whether the particular output (e.g., processed semiconductor wafers) have desirable properties.
Generally, the process engineer specifies or generates the model that includes the parameters for the process tool that will be used during wafer processing. The model specifies the various operating parameters used during the manufacturing process to generate a particular type of wafer output. The model is typically based on inspection of wafers by the process engineer and a determination of acceptable parameters based on the output of the process tool and the experience of the process engineer. After a particular process tool or chamber undergoes preventive or periodic maintenance, the values for acceptable parameters can change. A change in acceptable parameters generally requires the process engineer to manually re-specify the acceptable parameters for the particular tool or chamber, e.g., to re-create or re-enter the parameters of the model.
Creating a model in this manner is a relative lengthy and labor-intensive process, sometimes taking up to an hour or more. Additionally, the creation of a model requires the expertise or experience of a process engineer, which can lead to a certain percentage of faulty wafers based on human error or inconsistency in acceptable parameters between maintenance operations. Moreover, updating a model requires a similar labor-intensive process. A model may be updated as part of a periodic maintenance plan and/or in response to changes within the particular process tool. Updating the model typically requires adjustment or re-specification of the process parameters. The process engineer is typically involved in manually adjusting the parameters. The updated model takes approximately the same amount of time to update as a model created for the first time.